1. Field of the Invention
The present invention relates to a petroleum well for producing petroleum products. In one aspect, the present invention relates to systems and methods of electrically controlling downhole well interval inflow and/or injection for producing petroleum products.
2. Description of the Related Art
Attainment of high recovery efficiency from thick hydrocarbon reservoirs, requires uniform productivity from wells completed over long intervals.
In vertical wells, the open intervals typically include a number of geologic layers having a variety of petrophysical properties and initial reservoir conditions. Variations in permeability and initial reservoir pressure especially, result in uneven depletion of layers, if the layers are produced as a unit with a single draw-down pressure. As the field is produced, high permeability layers are depleted faster than tight layers, and high pressure layers may even cross-flow into lower pressure layers.
In horizontal wells, the open completion interval is usually contained in a single geologic layer. However, uneven inflow can result from a pressure drop along the well. This effect is particularly evident in long completion intervals where the reservoir pressure is nearly equal to the pressure in the well at the far end (the toe). In such a case, almost no inflow occurs at the toe. At the other end of the open interval near the vertical part of the well (the heel), the greater difference between the reservoir pressure and the pressure in the well results in higher inflow rates there. High inflow rates near the heel can lead to early gas breakthrough from gas coning down, or early water breakthrough from water coning up.
Productivity profiles of vertical wells are described by the steady state Darcy flow equation for radial flow:
                              q          R                =                              2            ⁢            π            ⁢                                                  ⁢            k            ⁢                                                  ⁢                          k              r                        ⁢            h            ⁢                                                  ⁢            Δ            ⁢                                                  ⁢            p                                μln            ⁡                          (                                                r                  e                                /                                  r                  w                                            )                                                          (        1        )            where                qR=flow rate [13t−1]        k=absolute permeability [12]        kr=relative permeability [unitless]        Δp=pressure draw-down=reservoir pressure-well pressure [m1−1t−2]        μ=viscosity [m1−1t−1]        re=outer radius of reservoir [1]        rw=well radius [1]        h=length of open interval [1]        
Each flowing fluid may be described by this equation. In most wells, we need to account for flow of the gas, oil, and water. In the initial phase of production of a field, reservoir pressure is usually large. If large draw-down pressures are applied, inflow profiles will be uniform for layers with similar permeabilities because variations in initial reservoir pressure of layers are usually smaller than the draw-down pressure. As the well is produced and layers are depleted, the reservoir pressure affects the productivity profiles to a greater extent because some layers may have a small draw-down, even if the well is produced at its lowest pressure. Variations in permeability among layers may arise from (1) differences in grain size, sorting, and packing, or (2) from interference of flowing fluids, i.e., the relative permeability. The former—grain mineral framework—is not expected to change the productivity profile very much during the life of the well because the grain framework remains unchanged, except for compaction. But compaction can equalize layer permeabilities. The effects of fluid saturation on permeability lead to poor productivity profiles because, for example, a high permeability layer is likely to have a high specific fluid saturation, which makes that layer even more productive. During the life of a well these saturation effects can lead to even poorer profiles because, for example, gas or water breakthrough into a well results in increasing breakthrough fluid saturation and even higher productivity of that fluid relative to the other layers.
Productivity profiles in horizontal wells may be affected by layering if the well intersects dipping beds or if the horizontal well is slightly inclined and crosses an impermeable bed. However, the major effect is expected to be the difference in draw-down pressure between the toe and the heel.
The problems associated with poor productivity profiles in wells with long interval completions have been addressed in a recent patent application entitled “Minipumps in a Drainhole Section of a Well”, filed 15 Sept. 1999, inventors M. E. Amory, R. Daling, C. A. Glandt, R. N. Worrall, EPC Patent Application no. 99203017.1, herewith incorporated by reference. This method proposes the use of several annular pumping devices located along the open interval of the well to offset the pressure drop due to flow in the well and thereby increase the inflow at the toe of the well.
Wells may also be used for fluid injection. For example, water flooding is sometimes used to displace hydrocarbons in the formation towards producing wells. In water flooding, it is desirable to have uniform injection. Hence with fluid injection, the same issues arise with respect to ensuring uniform injection as those mentioned above for seeking uniform inflow, and for the same reasons.
Conventional packers are known such as described in U.S. Pat. Nos. 6,148,915, 6,123,148, 3,566,963 and 3,602,305.
All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes, and indicative of the knowledge of one of ordinary skill in the art.